Stabilized polyamides

ABSTRACT

IN WHICH X DEVOTES A HYDROGEN RADICAL HAVING ONE OR TWO CARBON ATOMS.   =N-X-COOH   STABILIZATION OF POLYAMIDES BY ADDING OF IODINE COMPOUNDS AND COPPER COMPLEXES OF COMPOUNDS CONTAINING TWICE TO FOUR TIME THE STRUCTURAL UNIT:

United States Patent Oflice Patented Mar. 30, 1971 3,573,245 STABILIZEDPOLYAMIDES Gerhard Mueller, Limhurgerhof, Pfalz, and Hehnllt Doerfel andHans Wilhelm, Ludwigshafen (Rhine), Germany, assignors to BadischeAnilin- & Soda-Fabrik Aktiengesellschaft, Ludwigshat'en (Rhine), GermanyN Drawing. Filed Aug. 29, 1967, Ser. No. 663,942 Int. Cl. C08g 51/56U.S. Cl. 26045.75 Claims ABSTRACT OF THE DISCLOSURE Stabilization ofpolyamides by adding of iodine compounds and copper complexes ofcompounds containing twice to four times the structural unit:

in which X denotes a hydrocarbon radical having one or two carbon atoms.

It is known that polyamides can be stabilized against the effect of heatand air by adding compounds containing phenolic groups. The numerousphenolic compounds proposed for this purpose all have the disadvantage,however, that they discolor the polyamide upon prolonged action of heatin the presence of air. Discoloration of the polyamide often takes placeeven during the incorporation of these phenolic stabilizers.

Condensation products of aliphatic aldehydes with aromatic orcycloaliphatic amines have also already been recommended for stabilizingpolyamides. These stabilizers however also cause discoloration of thepolyamides.

Copper or compounds of copper, such as copper acetate, copper salts ofphosphoric acid and hypophosphoric acid, alone or in combination withcerium (III) and/or titanium (III) salts, have also been suggested asheat stabilizers for polyamides. The effect of the copper compounds canbe increased by using them in the form of copper complexes, either aloneor together with halogen compounds, particularly iodine compounds.Examples of compounds proposed for forming complexes are phosphoruscompounds and amines. These compounds however decompose duringpolycondensation, lower the degree of polycondensation of the polyamideor cannot be distributed homogeneously in the polyamide.

We have now found that polyamides can be stabilized against the effectof heat particularly effectively without the said disadvantages by usingas the stabilizing agent an iodine compound together with a coppercomplex of a compound which contains twice to four times the struc turalelement:

=N-X-C=O in which X denotes a hydrocarbon radial having one or twocarbon atoms.

The following are examples of compounds which may be used according tothis invention for preparing the copper complex: imidodiacetic acid,ethanolaminodiacetic acid, nitrilotriacetic acid, anilino-N,N-diaceticacid, cyclohexylenediamino N,N' tetraacetic acid, 2,6-diarninomethyl 4methylphenol N,N tetraacetic acid, N- methyldiethylenetriamino N,N"tetraacetic acid and his fi-aminoethyl) ether-N,N'-tetraacetic acid.

Tetraacetic acid derived from aliphatic and alicyclic 1,2-diamines, suchas ethylenediamine-N,N'-tetraacetic acid and1,2-diaminocyclohexane-N,N'-tetraacetic acid, and also the diacetic acidderived from ,B-aminoethanol, are particularly suitable.

Production of these acids and their complex copper salts form no part ofthe subject-matter of the present invention. The acids may be obtainedfor example by alkylation of ammonia or amines with a-halofatty acids orby condensation of carbonyl compounds with amines and hydrogen cyanidefollowed by hydrolysis of the nitrile group. The compounds may also beobtained by oxidation of ethanolamines.

The copper complexes used as stabilizers may be prepared by reaction ofthe acids with copper compounds, such as copper acetate or copperhydroxide. The copper complexes according to this invention contain inthe molecule carboxyl groups which are not utilized in the formation ofthe complex; they therefore behave as polyamideformers and may be whollyor partly condensed into the polyamides to be stabilized. In these casesthe stabilizers adhere particularly strongly to the polymers and cannotbe removed by extraction.

For the stabilization of the polyamides, 0.002 to 0.5%, preferably 0.01to 0.25%, of the copper complex is used, the optimum amount of thestabilizer used depending on its constitution and on the polyamide. Thecopper complexes may be used in the form of free acids or in the form oftheir alkali metal or amine salts. They are used in combination with aniodine compound, such as an alkali metal iodide, ammonium iodide, aniodide of a diamine or an organic iodine compound such as an iodolactam,for stabilizing polyamides in accordance with the process of theinvention. The iodine compounds may be used in an amount of one tohundred times the weight of the copper complex.

The mixture of copper complex and iodine compound to be used accordingto the process of the invention may be added to the polyamide-formingstarting materials prior to the formation of the polyamide or may beincorporated into the polyamide. The eifect of the new stabilizersystems extends to all polyamides and copolyamides from the knownpolyamide-forming compounds, such as lactams, diamines and dicarboxylicacids or aminocarboxylic acids.

It is a special advantage that the new stabilizers may be added to thepolyamide starting materials because they do not separate any copper orcopper oxide under the conditions of the polycondensation. They condenseinto the polyamide and are firmly bonded in the polymer so that in asubsequent extraction of the polycondensate for removal of monomers andoligomers, only very small amounts of stabilizer are removed. The newcopper complexes are superior to other copper compounds in that they donot result in any discoloration of the polyamide formed during thepolycondensation.

It is surprising that complexes in which the copper ions are so stronglymasked as they are in those used in accordance with this inventionshould have so excellent a stabilizing effect for polyamides against theeffect of heat. Owing to their stability, their effectiveness ismaintained even under prolonged action of heat at relatively hightemperatures.

Polyamides stabilized by the process according to this invention aresuitable for the production of moldings, films, sheeting, bands,ribbons, tapes and fibers for a great variety of purposes.

The following examples further illustrate the invention; the partsspecifield in the examples are parts by weight.

EXAMPLE 1 parts of the salt of adipic acid and hexamethylene diamine and40 parts of epsilon-caprolactam are polycondensed for three hours at 270C. with 20 parts of water, 0.017 part of the copper dipotassium salt ofethylenediaminetetraacetic acid and 0.15 part of potassium iodide. The Kvalue of the copolymer is 69 and rises to 3 86 after it has beenannealed for thre days at 140 C. in air. The light absorption (measuredin pressed plates 1 mm. in thickness) is 23% prior to annealing and 58%after three days. After this period, the polycondensate is notembrittled.

EXAMPLE 2 60 parts of the salt of adipic acid and hexamethylenediamineand 40 parts of epsilon-caprolactam are mixed with 20 parts of water,0.068 part of the copper-dipotassium salt of ethylenediaminetetraaceticacid and 0.9 part of potassium iodide and polycondensed as in Example 1.The K value of the polyamide is 71. The K value is 90 after the materialhas been left for three days at 140 C. in air. The light absorptionrises from 18% to 54% after the three-day heat treatment.

EXAMPLE 3 60 parts of the salt of adipic acid and hexamethy1ene diarnineand 40 parts of epsilon-caprolactam are mixed with 20 parts of water,0.028 part of the copper salt of ethylenediaminetetraacetic acid and 0.3part of potassium iodide and then poly-condensed as in Example 1. The Kvalue of the polycondensate is 73. After a heat treatment at 140 C. forthre days, the K value has increased to 87. The light absorption priorto the heat treatment is 26; after three days it is 61%. The polyamideis not embrittled after this treatment.

EXAMPLE 4 60 parts of the salt of adipic acid and hexamethylenediamineand 40 parts of epsilon-caprolactam are homogeneously mixed with 20parts of water, 0.055 part of the copper salt ofethylenediaminetetraacetic acid and 1.2 parts of potassium iodide andpolycondensed as descrbed in Example 1. A polycondensate is obtainedhaving a K value of 67 which rises to 87 after annealing for three daysat 140 C. in air. The light absorption is 15% and, after three days heattreatment, 53%.

EXAMPLE 5 The procedure of Example 1 is followed but with the additionaccording to the invention of 0.074 part of thecopper-hexamethylenediamine salt of ethylenediaminetetraacetic acid. Apolyamide is obtained having a K value of 69. Testing the resistance toheat at 140 C. in air gives a K value of 91 after three days storage.The light absorption prior to the heat treatment is 22 and after theheat treatment 43%. The polycondensate is not embrittled after thisperiod.

EXAMPLE 6 100 parts of caprolactam is polycondensed for three hours at270 C. with 20 parts of water, 0.074 part of thecopper-hexamethylenediamine salt of ethylenediaminetetraacetic acid and0.9 part of potassium iodide. The pressure is then released at 270 C. toremove excess steam and the product is condensed for three hours at 270C. in a stream of nitrogen. The polycondensate is granulated, boiled uptwice with water for twelve hours and dried. The K value of thepolycondensate is 68 and rises to 83 after storage for three days at 140C. and to 87 after ten days. The product is not embrittled after thisperiod.

EXAMPLE 7 100 parts of caprolactam is polycondensed with 20 parts ofwater, 0.08 part of the copper salt of nitrilotriacetic acid and 0.9part of potassium iodide as described in Example 6. The product isextracted and dried. The granulate is extruded into rods 50 x 6 x 4 mm.and stored in the air at 140 C. for three, five, seven and fourteendays. The rods are then conditioned for eight hours at 30 C. and 80%relative humidity. The impact strength of the annealed rods is testedaccording to DIN 53,453.

4 The rods show no fracture after hot storage for fourteen days.

EXAMPLE 8 100 parts of caprolactam is polycondensed with 20 parts ofwater, 0.065 part of the copper salt of1,2-diaminocyclohexane-N,N-tetraacetic acid and 0.9 part of potassiumiodide as described in Example 6, extracted and dried. The product isextruded into rods 50 x 6 x 4 mm. and annealed, conditioned and testedaccording to DIN 53,453 as in Example 7. After storage for fourteen daysat 140 C., the polycaprolactam is still so tough that no fractureoccurs.

EXAMPLE 9 The procedure of Example 8 is followed, but only 0.006 part ofthe copper salt of 1,Z-diaminocyclohexane-N,N tetraacetic acid and 0.09part of potassium iodide are added. A polyamide is obtained which showsno fracture after storage for fourteen days While heating and testingaccording to DIN 53,453.

EXAMPLE 10 The procedure of Example 10 is followed with an addition of0.006 part of the copper salt of ethanolamine- N,N-diac'etic acid and0.09 part of potassium iodide. A polyamide is obtained having the sameheat resistance as described under Example 10.

EXAMPLE 12 parts of polycaprolactam is mixed with 1.065 parts of thecopper salt of ethanolamine-N,N-diacetic acid and 0.3 part of potassiumiodide in a high-speed mixer and the product processed in a commercialextruder. The polyamide granulate is dried and extruded into rods 50 x 6x 4 mm. which are stored for three to fourteen days in the air at C. andthen for eight hours at 30 C. and 80% relative humidity. Tests of theimpact strength according to DIN 53,453 did not cause fracture.

We claim:

1. A composition of matter stabilized against heat and light comprisinga synthetic linear polyamide having recurring groups in the main chainof the molecule, there being incorporated in said polyamide astabilizing mixture of: (a) about 0.002 to 5% by weight, with referenceto the polyamide, of a copper complex of an organic compound selectedfrom the class consisting of monoamines hearing at least two CH -COOHsubstituents on the nitrogen atom and diamines in which each terminalnitrogen atom bears two substituents thereon; and

(b) about 0.002 to 2.5% by weight, with reference to the polyamide, ofan iodide selected from the class consisting of alkali metal iodides,alkaline earth metal iodides and ammonium iodide.

2. A composition as claimed in claim 1 wherein com- References CitedPollen; (b) is Potassium f 1 1 h UNITED STATES PATENTS 3. composition asc aime in c aim w erein comv ponent (a) is a copp r complex ofethylenediamine-N,N'-

$332 322 2; tetracetl" acld- 5 3,313,769 4/1967 Ma-ahs 260-4515 4. Acomposition as clalmed in claim 1 Wherem component (a) is a coppercomplex of ethanolamine-N,N'- DONALD E. CZAJAPTimaW Examiner diaceticacid.

5. A composition as claimed in claim 1 wherein com- HOKE AssistantExaminer ponent (a) is a copper complex of LZ-diaminocyclo- 10 U5. CLhexane-N ,N-tetraacetic acid, 260 4v5 7? 453, g;

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3.575.245 Dated March 3OL 1971 Inventor) Gerhard Mueller et a1 It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 1, line 7, insert Claims priority, application Germany, September9, 1966, P 15 95 342.1

Column 2, line 64, "specifield" should read specified Column 3, line 25,"thre" should read three line 36, "scrbed" should read scribed Signedand sealed this 11 .1511 day of September 1971.

(SEAL) Attest:

ROBERT GOTTSCHALK A a mmmwcasa JR. HDW R1 Actlng commlssloncr of PatAttesting Officer

